1. Field of the Invention
The present invention relates to a recording medium on which information is recorded, and a head that reads information recorded in the recording medium, and more particularly, to a method of estimating life of the head and the recording medium.
2. Description of the Related Art
When an information recording and reproducing apparatus (hereinafter, “magnetic disk apparatus”), which uses a magnetic disk as a recording medium to record information (data), reads information from the magnetic disk, it is common to use a magnetic head that uses giant magneto resistive effect from a giant-magneto-resistive (GMR) element or a ferromagnetic tunneling effect from a tunneling-magneto-resistive (TMR) element.
The magnetic disk apparatus is used as a storage apparatus for various systems such as a computer, a personal computer, or a server to perform reading and writing of information repeatedly. However, when the magnetic head is used for a long time, the GMR element or the TMR element degrades and an output of the magnetic head gradually decreases, which may result in occurrence of a data-read error.
Conventionally, various techniques have been proposed regarding the degradation of the magnetic head using the GMR element. For example, A. J. Wakkash N. Cheng, IEEE Trans. Mag. 35-5, 2610-2712 (1999) discloses a technique to cope with the degradation of the GMR head (magnetic head), focused on temperature. In I. F. Tsu, G. a. Burg, and W. P. Wood, IEEE Trans. Mag. 37-4, 1707-1709 (2001), a technique to cope with the degradation of the GMR head (magnetic head), focused on magnetic field, has been disclosed.
In recent years, a recording density in a magnetic disk increases, and a floating amount of a magnetic head decreases to about 10 nanometers. Ideally, the magnetic disk should be flat; however, there is actually a fine undulation on the magnetic disk. When data is read from the magnetic disk with a floating amount of about 10 nanometers, the magnetic head receives an impact from a contact between the magnetic head and the magnetic disk due to the fine undulation on the magnetic disk. Even if a magnitude of the impact is small, a life (degradation) of the magnetic head is influenced by the impact.
In the above conventional techniques, however, the impact due to the contact between the magnetic disk and the magnetic head has not been considered. Therefore, the degradation of the magnetic head cannot be estimated properly.
In a conventional method of inspecting the magnetic disk, in general, the maximum value of the magnitude of the impact that a magnetic disk receives is often used. However, when the frequency of contacts increases, even if the magnitude of each impact is small, the life of the magnetic head is influenced by the impact. Therefore, in the conventional method of inspecting the magnetic disk utilizing the maximum value of the magnitude of the impact, since an accumulation of the magnitude of the impact with time is not taken into consideration, a proper inspection of the magnetic disk can not be performed.
There are various materials used for an element to read data in the magnetic head. Durability against the impact due to the contact between the magnetic disk and the magnetic head varies according to each material or a structure of the magnetic head. In the conventional techniques, however, measuring and evaluating the durability of the magnetic head including the magnitude of the impact between the magnetic disk and the magnetic head have not been considered. Accordingly, a difference in the durability of the magnetic head against the contact between the magnetic head and the magnetic disk cannot be properly evaluated.